Tramadol Pharmaceutical Formulations
Tramadol hydrochloride (HCl) was developed by Grünenthal GmbH, Germany. It has been marketed in Germany since 1977 (eg. Tramal™), and in the United States as Ultram® since 1995. The efficacy and safety profile of tramadol HCl make it highly suitable as a long-term treatment for chronic pain.
Tramadol HCl is a synthetic, centrally acting analgesic that has been shown to be effective in a variety of acute and chronic pain states. In particular, tramadol HCl, in both immediate and slow-release formulations, in conjunction with non-steroidal anti-inflammatory drugs (NSAIDs) (Roth S H “Efficacy and safety of tramadol HCl in breakthrough musculoskeletal pain attributed to osteoarthritis”. J. Rheumatol 1998; 25:1358-1363. Wilder-Smith C H et al. “Treatment of severe pain from osteoarthritis with slow-release tramadol or dihydrocodeine in combination with NSAID's: a randomized study comparing analgesia, antinociception and gastrointestinal effects”. Pain 2001; 91:23-31.), has been demonstrated to reduce pain attributed to osteoarthritis (OA). After oral administration, tramadol HCl is rapidly and almost completely absorbed, and it is extensively metabolized. The major metabolic pathways appear to be N- and O-demethylation and glucuronidation or sulfonation in the liver. Only one metabolite, mono-O-desmethyltramadol (M1), is pharmacologically active, which has an approximate 200-fold higher affinity for the μ-opioid receptor than racemic tramadol (DeJong R. “Comment on the hypoalgesic effect of tramadol in relation to CYP2D6” (comment) Pain Dig 1997; 7:245; Kogel B. et al “Involvement of metabolites in the analgesic action of tramadol” Proc. 9th World Congress on Pain, Vienna, 1999). In healthy humans, tramadol is demethylated by the polymorphic enzyme cytochrome P450 2D6 (CYP2D6) to the M1 metabolite.
The mechanism of action of tramadol HCl is not completely understood. Animal models indicate that the drug (and its active M1 metabolite) acts as an opiate agonist, apparently by selective activity at the μ-receptor. In addition to opiate agonist activity, tramadol HCl inhibits re-uptake of certain monoamines (norepinephrine, serotonin) which appears to contribute to the drug's analgesic effect. The antinociceptic effect of tramadol HCl is only partially antagonized by naloxone in some tests in animals and humans. In addition, because of the drug's opiate agonist activity, it has been suggested that tramadol HCl may produce dependence; however, its abuse potential appears to be low, and tramadol HCl is not “subject to control” under the United States Federal Controlled Substances Act of 1970 as a scheduled drug.
Immediate release formulations of tramadol HCl are well known in the art. Such formulations, however, require frequent dosing in order to provide effective pain relief. Lack of compliance with high frequency dosing regimens can result in inconsistent plasma drug concentrations and accordingly less consistent analgesia. Twice daily formulations are available and are desirable over immediate release formulations as they provide longer periods of analgesia after administration and require less frequent dosing. A once daily formulation is even more desirable for increased effectiveness, safety and convenience.
A critical factor influencing the rate of absorption, and thereby the safety and efficacy, of an active pharmaceutical ingredient by the body following oral administration in a tablet or other solid dosage form is the rate of release of the active pharmaceutical ingredient from that dosage form post ingestion.
It is thus the ability of the dosage form components to control the release rate that constitutes the basis for the so-called controlled-release, extended-release, sustained-release or prolonged-action pharmaceutical preparations that are designed to produce slow, uniform release and absorption of active pharmaceutical ingredients over a period of hours, days, weeks or months. The advantages of such controlled-release formulations include: a reduction in the required administration frequency of the drug as compared to conventional immediate release dosage forms, often resulting in improved patient compliance; the maintenance of a stable concentration of the drug in the body and thereby a sustained therapeutic effect over a set period of time; and a decreased incidence and intensity of undesired side effects of the active agent caused by the high plasma concentrations that occur after administration of immediate-release dosage forms.
Many materials have been proposed and developed as matrices for the controlled release of active pharmaceutical ingredients. These include, for example, polymeric materials such as polyvinyl chloride, polyethylene amides, ethyl cellulose, silicone and poly(hydroxymethyl methacrylate). See e.g., U.S. Pat. No. 3,087,860 to Endicott et al; U.S. Pat. No. 2,987,445 to Levesque et al.; Salomon et al. Pharm. Acta Helv., 55, 174-182 (1980); Korsmeyer, Diffusion Controlled Systems: Hydrogels, Chap. 2, pp 15-37 in Polymers for Controlled Drug Delivery, Ed Tarcha, CRC Press, Boca Raton, Fla. USA (1991); and Buri et al., Pharm. Acta Helv. 55, 189-197 (1980).
High amylose starch has also been used for controlled-release purposes and, in particular, recent advances have been made using cross-linked high amylose starch. For example, U.S. Pat. No. 6,284,273 (Lenaerts et al.), which issued Sep. 4, 2001, and No. 6,419,957 (Lenaerts et al.), which issued Jul. 16, 2002, teach a solid controlled release oral pharmaceutical dosage unit in the form of tablets comprising a dry powder of a pharmaceutical product and a dry powder of cross-linked high amylose starch, wherein said cross-linked high amylose starch is a matrix comprising a mixture of about 10-60% by weight of amylopectin and about 40-90% amylose. U.S. Pat. No. 6,607,748 (Lenaerts et al.) which issued on Aug. 19, 2003 describes a process for making a cross-linked high amylose starch which is known under the name Contramid®.
Extended Release Formulations Known in the Art
Extended and controlled release formulations relating to tramadol HCl have been suggested, examples being described in: United States Patent Application Publication No. 2003/0143270, (Deboeck et al.) published Jul. 31, 2003; U.S. Pat. No. 6,254,887 (Miller et al.) issued Jul. 3, 2001; United States Patent Application Publication No. 2001/0036477 (Miller et al.) published Nov. 1, 2001; U.S. Pat. No. 6,326,027 (Miller et al.) issued Dec. 4, 2001; and U.S. Pat. No. 5,591,452 (Miller et al) issued Jan. 7, 1997; and European Patent No. 1 190 712 (Vanderbist) published Mar. 27, 2002.
Although there are some controlled release tramadol HCl formulations on the market which purport to be once-daily formulations, none of these has successfully replaced twice-daily tramadol HCl formulations.
Articles have been published in which comparative data between putative “once-daily” tramadol HCl formulations and immediate release tramadol HCl formulations are presented. Adler et al., “A Comparison of Once-Daily Tramadol with Normal Release Tramadol in the Treatment of Pain in Osteoarthritis,” The Journal of Rheumatology (2002) 29(10): 2195-2199; and Bodalia et al., “A Comparison of the Pharmacokinetics, Clinical Efficacy, and Tolerability of Once-Daily Tramadol Tablets with Normal Release Tramadol Capsules,” Journal of Pain and Symptom Management (2003) 25(2): 142-149.
Adverse Events from Administration of Tramadol HCl
The most frequently reported side effects of tramadol observed in clinical trials in the United States are constipation, nausea, dizziness/vertigo, headache, somnolence and vomiting. These are typical adverse effects of opiate drugs. Seizures and anaphylactoid reactions have also been reported, though the estimated incidence of seizures in patients receiving tramadol HCl is less than 1% (Kazmierczak, R., and Coley, K.: “Doctor letters on prescribing: evaluation of the use of tramadol HCl.” Formulary 32: 977-978, 1997).
Adler et al., supra, reports on the results of a clinical study comparing a once daily tramadol formulation to immediate release tramadol in the treatment of pain in osteoarthritis. The authors report similar adverse event profiles for individuals in both treatment groups. Table 2 of Adler et al. indicates that a greater percentage of people who were in the once daily treatment group withdrew due to adverse events than did those in the other treatment group.
In Bodalia et al., supra, the authors report comparable tolerability with a 150 mg once daily dose, a 200 mg once daily dose and three doses of a 50 mg normal release tramadol formulation. This article does not however include any information on how to make the formulations which are purported to be “once daily” nor does the article disclose any pharmacokinetic data after a single dose.
Citation or identification of any reference in this section shall not be construed as an admission that such reference is available as prior art to the present invention.